Conventional survivability systems are computer-based systems for detecting and navigating aircraft around detected threats. In planning the route of an aircraft's mission, known threats such as hostile ground fire, military positions, etc., are taken into account. The planned route, which may be stored in the aircraft's computer system, includes a starting point, a number of intermediate waypoints, and an ending point. The distance between each waypoint may be measured in nautical miles and referred to as a leg. Thus, a conventional planned route consists of a number of connected legs that angle around known threats to provide a safe route between the aircraft's starting point and its ultimate mission destination (endpoint). The conventional route is planned such that there is no “threat intervisibility,” i.e., the aircraft being visible by the threat. Visible may include acoustic, visual, infrared, radar, or other suitable means of detection.
However, conventional route planning must also take into account the problem of unplanned threats, unknown at the time, which might “pop up” during the mission. When an unknown threat appears, steps must be taken to avoid detection by the threat without compromising the mission's objectives.
One conventional approach to this problem is inflexible. When an unknown threat pops up during a mission, the aircraft's computer system automatically directs the aircraft to change course and steer along one of a number of predetermined evasive legs. While the aircraft is changing course, the system attempts to recognize the threat and to calculate the intervisibility of the threat. If a planned route intersects the threat's intervisibility, then a route change is calculated from the end of the evasive leg to a next waypoint. If the proposed route change still intersects the threat's intervisibility, then a second route change is calculated from the end of the evasive leg to a following waypoint, and so forth. This approach limits the options of the aircraft operator, forces evasive maneuvers that are not optimized for an unknown threat, and is often slow.
Another conventional approach rapidly responds to unknown threats in a timely and safe manner. This approach provides quicker decisions when required for close-range threats and also flexibility to choose a response when time permits.
With this conventional approach, a previously unknown threat is detected. It is then determined whether the aircraft's planned route intersects intervisibility with the threat. If not, the planned route is maintained. If it is determined that the two will intersect, then the response depends on the current distance of the intersection from the aircraft. If the intersection is less than a predetermined distance, a route change is automatically executed. If the intersection is greater than the predetermined distance, the aircraft has time to maneuver and the aircraft operator is notified. Meanwhile, the severity of the threat is also checked against possible altitudes to determine if the planned route may be “cleared,” i.e., maintained at a lower, acceptable flying altitude. If an acceptable altitude exists, the aircraft operator is permitted to choose between the planned route and an alternative route. Thus, the operator is permitted to manually respond to a threat where such permission does not endanger the aircraft.
These conventional approaches intend to prevent an intersection between a route of an aircraft and the detection capability of any possible threats. This is an absolute rule inherent in these approaches. These approaches do not consider the elapsed time required between initial detection of the aircraft by a threat and the threat's actually ability engage and fire upon the aircraft.